Build an “On/Off” Switch into any complicated machinery/factories you build, and only leave them on when absolutely necessary. If you’re planning to be away from Minecraft for a long while, turn everything off.

Close Dynmap in your web browser when you are not using it.

BuildCraft

Use RedPower pipes instead of Buildcraft pipes where possible, as these are smarter, accident proof, and less demanding on the server.

Remove quarries and filling machines as soon as they are done with their tasks. These cause a significant amount of lag, and performance issues while the black & yellow “construction box” around the area in which these machines work still exists.

IndustrialCraft

NEVER create loops in electrical circuits, as this will cause issues where the server dedicates a lot of time towards performing pointless arithmetic in distributing the electricity. Wire layouts should always be linear (although they can branch). If you use a lot of wires close together and want to stop them connecting, use a PAINTER to paint the wires different colours so that they will not connect.

Don’t connect different types of wires. If you need to use multiple types of wires, have something to brisde the gap rather than connecting them directly (such as a Batbox, MFFE or MFSU).

RedPower

Use as few timers/sequencers as possible, and don’t operate them faster than 2.0s

Chunk Loaders

Don’t use World Anchors or Teleport Tethers to keep chunks loaded (World Anchors used to make Anchor Carts are ok). Instead, use Dimensional Anchors, and set the radius to as small as possible.

Although there is an overly-generous per-player allowance for how many chunks you can keep loaded, please try to keep these to a minimum, and remove any old chunk loaders that you no longer use, or are not using for prolonged periods of time.